Alcoholism is the most prevalent and widespread of all addictive diseases and development of effective treatments is a world-wide priority. Only three drugs have been approved by the FDA for the treatment of alcohol dependence: disulfiram (antibuse), acamprosate, and naltrexone (Trexan or Revia) and, of these, naltrexone (NTX) is the most effective. Yet NTX is under- utilized in clinical treatment settings because the efficacy of NTX is modest, it is not effective for all alcoholics and, when it is effective, a significant number of alcoholics fail to maintain initial treatment gains and subsequently relapse to heavy drinking. There is a pressing need for additional medications to treat alcohol abuse, dependence and relapse. The long-term objective of this proposal is to increase the number of drugs available to treat alcohol abuse and alcoholism. Both the opioid and acetylcholinergic systems in the brain play important roles in mediating alcohol drinking. Our preliminary studies indicate that acute oral treatment with either naltrexone (NTX), a nonspecific opioid receptor antagonist, or varenicline (V), an 42 nicotinic acetylcholinergic receptor partial agonist, decreases alcohol intake in alcohol-preferring (P) rats that have been selectively bred for high voluntary alcohol drinking. The question now is whether these two drugs are effective over the course of prolonged treatment, and whether combining these two drugs into a single oral medication enhances the effectiveness, or prolongs the duration of action, of the combination when compared with either drug alone. The research design uses a voluntary oral drug consumption method that we developed which allows us to assess the efficacy of drugs over long periods of time. Our hypothesis is that NTX and V will act either additively or synergisticall to more effectively reduce alcohol drinking than can either drug alone. The specific aims of this proposal are to determine whether a combination of NTX + V is more effective than is either drug alone: 1) in decreasing ongoing alcohol drinking in rats selectively bred for alcohol preference and high alcohol intake (P rats), 2) in blocking the initiation/acquisition of alcohol drinking in P rats and 3) in blocking the increase in alcohol drinking that occurs following reaccess to alcohol following alcohol deprivation (alcohol deprivation effect of ADE, an animal model of alcohol relapse) in P rats. Mechanistic studies will determine whether NTX + V alters the rewarding/reinforcing properties of alcohol and/or alcohol clearance [[or drinking-induced BACs]]. The significance of the proposed work is that the results may lead to a new pharmacotherapeutic approach to the treatment of alcohol abuse, alcohol dependence and relapse; an approach that may be particularly valuable for treating alcoholics who do not respond to treatment with the medications currently available.